There's no need to manually convert it. Once the useddsfanart option is set to true via advancedsettings.xml, it will be handled automagically while browsing/caching the library

Always read the online manual(wiki), FAQ(wiki) and search the forum before posting. Do not PM or e-mail Team-Kodi members directly asking for support. Read/follow the forum rules(wiki).
Please read the pages on troubleshooting(wiki) and bug reporting(wiki) before reporting issues.

Ideally 'userdata/thumbnails' is ONLY touched from core. Add-ons usually store their data in the addon_data folder. Anyway, i think you should open a new thread for this _special_ issue.

Always read the online manual(wiki), FAQ(wiki) and search the forum before posting. Do not PM or e-mail Team-Kodi members directly asking for support. Read/follow the forum rules(wiki).
Please read the pages on troubleshooting(wiki) and bug reporting(wiki) before reporting issues.

I was wondering if someone would be kind enough to write a batch file (for WINDOWS) to convert all the .tbn files in the fanart directory to dds. nvcompress or makedds will work since I have both executables.

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